A conventional crawler type traveling vehicle which can travel by having a drive wheel and an idler wheel (driven wheel) disposed in front and rear positions on each side of a body frame as a lower structure and having an endless crawler belt wound around these drive and idler wheels is known as a vehicle, mainly used for work on rough terrain, such as a construction machine (e.g. a bulldozer or a hydraulic excavator), a materials handling machine or an agricultural machine. In this crawler type traveling vehicle, a plurality of rollers are placed at required intervals between the drive wheel and the idler wheel above a non-ground-contact surface of the crawler belt and is supported by the body frame for ensuring ground contact force during traveling and stably supporting a vehicle body.
Typically, as shown in FIGS. 6 and 7, such roller 50 of the crawler belt is rotatably supported on support shaft 52 via bearing bush 53. Support shaft 52 has both ends fixedly supported by large bogie 60 via respective small bogies 61. Large bogie 60 is swingably mounted to track frame (body frame) 62. Bearing bush 53 is fixedly fitted to an inner peripheral surface of roller 50 and is in contact with a rotation supporting part of support shaft 52. Accordingly, oil feeding passages 54, 54a are formed in support shaft 52 to supply lubricating oil toward a bearing surface of bearing bush 53, and oil reservoir 51 is formed inside roller 50. The lubricating oil is supplied from this oil reservoir 51 to the bearing surface, thus forming an oil film. To prevent this lubricating oil from leaking out with rotation of roller 50, seal mechanism 56 is provided between each outer face section of roller 50 and support shaft 52. A part of seal mechanism 56 that faces roller 50 is supported by seal supporting piece 57 provided at the outer face section of roller 50. For bearing axial thrust acting on roller 50, thrust bearing 58 is placed between inner surface 57a of seal supporting piece 57 and thrust bearing surface 52a of support shaft 52. Seal supporting piece 57 has a flange mounted to the outer face section of roller 50 by a plurality of bolts 59. Bolts 59 for mounting this seal supporting pieces 57 are tightened by being screwed into respective screw holes 59a of roller 50.
Another conventional roller for a tracklaying vehicle using a rubber crawler belt is disclosed, for example, in Japanese Utility Model Unexamined Publication No. H04-078086 (FIGS. 9 and 10).
As mentioned earlier, conventional roller 50 requires a plurality of screw holes 59a for mounting thrust bearing 58 and seal supporting piece 57, which forms a part of seal mechanism 56, to each of its outer face sections, thus having many problems associated with workability.
In other words, since a heavy load acts on roller 50 via crawler belt 63, roller 50 is heat-treated for increased strength of its outer peripheral surface. Making screw holes 59a before the heat treatment can be done with relative ease, but free oxides (rust) are produced on the surface of screw holes 59a by the heat treatment and need to be removed. The removal of the oxides on the plurality of screw holes 59a involves a lot of trouble and increases the cost of working. Drilling screw holes 59a after the heat treatment of roller 50 eliminates the trouble of removing the rust, but requires a drill or a tap that can drill even material having a high hardness because the roller which is heat-treated has increased hardness. Consequently, the cost of drilling increases.
The conventional rollers, including the one disclosed in Japanese Utility Model Unexamined No. H04-078086, each need to be constructed to include oil reservoir 51 for supplying the lubricating oil to the bearing part. To define oil reservoir 51, roller 50 is split into left and right pieces 50a, 50b, and these pieces 50a, 50b are joined together at an axially center section by weld a. Because of welding that is required, the cost of working increases. This inevitably leads to increased costs.
The present invention addresses such problems and aims to provide a roller for a crawler type traveling vehicle. This invention aims to streamline the manufacture of the roller by simplifying a structure for holding a seal mechanism between a bearing part and the outside and a structure for a thrust bearing and facilitating working while eliminating the need for welding.